This invention relates to heat-sealing flexible closures onto containers which have rims or flanges around their mouths.
It has been known to heat-seal a flexible closure onto the rim of a plastics container containing, for example, a food product, one such process being described and claimed in Applicants' UK Patent No. 2067157. In commercial exploitation of the invention of Patent No. 2067157 Applicants have made the container of polypropylene with an intermediate barrier layer for oxygen resistance, and for the closure material have proposed a laminated material of aluminium foil laminated to a layer of HDPE (high density polyethylene) for sealability. In use, the closure is heat sealed onto the container rim with the HDPE side of the closure material in contact with the polypropylene upper surface of the container rim. However, the seal achieved has not been manually peelable, that is to say, it has been necessary for the consumer to cut the closure material inside the rim in order to open the sealed container.